Remotely
Sensed DataThe
module contains a number of remotely-sensed images. These images were
taken by a satellite that senses electromagnetic energy (light) in different
wavelengths. The images are not "photos," even though they appear to be
very much like photos except for their color. Typically, the color of
the images is a "false" color that enhances some feature.

Remember
that film in a camera captures electromagnetic wavelengths we call visible
light. These are the same wavelengths that your eyes sense. Other wavelengths
also can be sensed. Landsat and other satellites have instruments that
can sense these other wavelengths. Remote
sensing is more than an extension of our five senses. It provides us with
information that is ordinarily invisible to us because it cannot be sensed
by our eyes or because it is hidden from our view or would be dangerous
for us to acquire.

Remote sensing
from space is particularly important in helping us find ancient impact
sites, where Earth was hit by asteroid/comet-like bodies. When we stand
on Earth, we don't have the vantage point necessary for seeing these very
large and usually highly eroded, craters. By analogy, if we put our hands
over our eyes, we cannot see that they are hands, but if we get a more
remote view by moving our hands 4 or 5 inches away from our face, we can
tell their shape.

Remote sensing
on Earth, through the use of seismic (sound vibrations) waves, has enabled
us to find older craters that lie buried under layers of younger sedimentary
rocks. The most famous example of this kind is the Mexican (Yucatan Peninsula)
crater called Chixulub, which may have been made at the time of the last
dinosaurs.

Remote sensing
also helps us to know our present situation in the Solar System. A small
group of individuals have devoted themselves to searching the sky for
Near Earth Objects (NEOs). These objects may be like those that have cratered
Earth. Sometimes these objects are detected as they pass by us. They travel
at high speeds and would cause devastation if they were to hit Earth.